This disclosure relates to a lubrication method and apparatus for lubricating fan shaft bearings in a gas turbine engine.
A gas turbine engine includes a fan section with a fan shaft that is mounted on bearings to rotate fan blades. The fan shaft is rotatable about an axis and the bearings include a fore bearing and an aft bearing that is spaced rearwardly from the fore bearing along the axis. A seal plate is fixed to the fan shaft and is positioned forwardly of the fore bearing. A bearing spacer is fixed to the fan shaft and is positioned between inner races of the fore and aft bearings. Inner surfaces of the bearing races and the bearing spacer, and an outer surface of the fan shaft, include axial slots that are formed to extend in a direction along the axis.
A spray bar is positioned within the fan shaft and includes a pair of supply jets. A supply dam is formed on the fan shaft and is positioned between the pair of supply jets. The fan shaft also includes holes that provide fluid to the spacer and to the aft bearing. The holes are staggered with the slots in the fan shaft and bearing spacer to distribute lubricating fluid to the fore bearing and the seal plate.
The supply dam and supply jets cooperate to direct fluid toward an inner surface of the fan shaft and the supply holes; however it is difficult to control apportionment of the lubricating fluid. Further, apportionment can change with different engine operation points, which is not desirable. Thus, some holes may not receive enough lubrication fluid while other holes may receive too much.
Also, the amount of lubricating fluid supplied is determined by the number of slots and the number and size of the holes. When the amount of lubrication needs to be varied, the fan shaft and bearing spacer have to be reconfigured to adjust the number of slots and holes, and/or the size of the holes. Further, it is difficult and time consuming to properly clock the slots relative to the holes during assembly of the bearing spacer onto the fan shaft.
Accordingly, there is a need to provide an improved lubrication system that can precisely lubricate the bearings and seal plate, as well as addressing the other short comings discussed above.